The present invention relates to a method and apparatus for making note books or pads whose leaves or sheets have straight rows of marginal perforations for reception of spiral binders which hold the leaves together. More particularly, the invention relates to a method and arrangement for manipulating marginally perforated note books or pads prior to insertion of metallic or plastic spirals which are thereupon transformed into spiral binders. The spirals are actually circular helices, i.e., they resemble space curves traced on a cylinder. However, such bodies are popularly known as spirals and the binders which are obtained by subdivision and trimming of metallic or plastic circular helical bodies are commonly known as spiral binders. Therefore, the following description will refer to spirals and spiral binders with the understanding that the spirals are circular helices.
In presently known apparatus for the production of so-called spiral binder note books or pads, the holes consisting of registering perforations in the leaves or sheets are converted into arcuate passages for convenient introduction of the leader of a spiral by shifting the leaves relative to each other so that each originally straight hole assumes an arcuate shape. To this end, a profiling device is caused to move against the rear edge face of a note book and to thereby effect an appropriate displacement of neighboring sheets relative to each other. That surface of the profiling device which engages the rear edge face of the note book has a curvature matching the curvature of the convolutions of a metallic spiral which is thereupon threaded through the perforations of the sheets. A drawback of such arrangement is that predictable shifting of sheets which form a pad is insured only when the note books are relatively thin and/or when the size of the sheets is small.
It is also known to employ the profiling device in combination with arcuate prongs which are introduced into the holes of a note book prior to engagement of the rear edge face of the note book with the profiling device. The curvature and helix angle of the prongs equal or approximate those of the convolutions of a spiral. Since the prongs are introduced into straight holes, the sheets must be formed with large-diameter perforations, especially, if the diameter of the spiral is relatively small. Such apparatus, too, fail to insure that the leader of a spiral will invariably find its way during threading through the perforations of a pile of sheets which form a note book.